在 PowerShell 中返回具有单个元素的数组

Question

这应该很简单——我需要从一个函数返回一个哈希表数组。这在有多个哈希表时有效，但当只有一个时，结果不是数组。我宁愿不测试结果是否为数组。

function GetArrayWith1Hashtable()
{
    $array = @()

    $hashtable = @{}
    $hashtable["a"] = "a" 
    $hashtable["b"] = "b" 
    $hashtable["c"] = "c"
    $array += $hashtable 

    Write-Host "GetArrayWith1Hashtable array.Length =" $array.Length
    Write-Host "GetArrayWith1Hashtable array.Count" $array.Count
    Write-Host "GetArrayWith1Hashtable array[0].Keys" $array[0].Keys

    $array
}

function GetArrayWith2Hashtables()
{
    $array = @()

    $hashtable = @{}
    $hashtable["a"] = "a" 
    $hashtable["b"] = "b" 
    $hashtable["c"] = "c"
    $array += $hashtable 

    $hashtable2 = @{}
    $hashtable2["d"] = "d" 
    $hashtable2["e"] = "e"
    $hashtable2["f"] = "f"
    $array += $hashtable2 

    Write-Host "GetArrayWith2Hashtables array.Length = " $array.Length
    Write-Host "GetArrayWith2Hashtables array.Count = " $array.Count
    Write-Host "GetArrayWith2Hashtables array[0].Keys =" $array[0].Keys
    Write-Host "GetArrayWith2Hashtables array.Count = "$array[1].Keys

    $array
}

$result1 = GetArrayWith1Hashtable
# $result1.Length - not available
Write-Host "Result of GetArrayWith1Hashtable result1.Count = " $result1.Count                      # Count = 2 (would expect this to be 1)
# $result1[0] not available - not an array

$result2 = GetArrayWith2Hashtables
Write-Host "Result of GetArrayWith2Hashtables result2.Length = "    $result2.Length # Length = 2
Write-Host "Result of GetArrayWith2Hashtables result2.Count = "     $result2.Count # Count = 2
Write-Host "Result of GetArrayWith2Hashtables result2[0].Keys = "     $result2[0].Keys # Keys = c a b
Write-Host "Result of GetArrayWith2Hashtables result2[1].Keys = "     $result2[1].Keys # Keys = d e f

 <#
  FULL OUTPUT:

 GetArrayWith1Hashtable array.Length = 1
 GetArrayWith1Hashtable array.Count 1
 GetArrayWith1Hashtable array[0].Keys c a b

 Result of GetArrayWith1Hashtable result1.Count =  2

 GetArrayWith2Hashtables array.Length =  2
 GetArrayWith2Hashtables array.Count =  2
 GetArrayWith2Hashtables array[0].Keys = c a b
 GetArrayWith2Hashtables array.Count =  d e f

 Result of GetArrayWith2Hashtables result2.Length =  2
 Result of GetArrayWith2Hashtables result2.Count =  2
 Result of GetArrayWith2Hashtables result2[0].Keys =  c a b
 Result of GetArrayWith2Hashtables result2[1].Keys =  d e f

 #>

Answer 1

只需将返回类型转换为数组即可：

$result1 = @(GetArrayWith1Hashtable)

Answer 2

实际上，您只需在退回的商品前添加一个逗号，就像这样。这告诉 PowerShell 按原样返回它，而不是试图对它变得聪明。这还允许您在一个地方修复它，而不是在调用它的任何地方。

function GetArrayWith1Hashtable()
{
    $array = @()

    $hashtable = @{}
    $hashtable["a"] = "a" 
    $hashtable["b"] = "b" 
    $hashtable["c"] = "c"
    $array += $hashtable 

    Write-Host "GetArrayWith1Hashtable array.Length =" $array.Length
    Write-Host "GetArrayWith1Hashtable array.Count" $array.Count
    Write-Host "GetArrayWith1Hashtable array[0].Keys" $array[0].Keys

    # The only edit was to add the comma below
    ,$array
}

更新：虽然我不认为你想要这个功能，但我还是会提到它，以便其他人了解差异并为他们的方法做出明智的选择。

为了让您的函数兼容以便在管道中更有效地使用，更好的方法是为每个项目调用 Write-Object。

function GetArrayWith1Hashtable()
{
    Write-Object "a" 
    Write-Object "b" 
    Write-Object "c"
}

通过使用 Write-Object，您允许 PowerShell 分别为每个对象调用管道中下一个命令的 Process block。否则它将调用下一个命令并将单个数组对象传递给它。你可以阅读更多关于piping objects here